Kveikur reportedly marks the beginning of a more “aggressive” sound for Iceland’s Sigur Rós. It seems naive – though exciting – to predict that, after the success of their last two albums (perhaps their most accessible and “mainstream” to date), the band might fall back into relying solely on harsh, full-blown, Godspeed!-esque post-rock. Yet almost anything with rhythm would sound more energetic than the heart-wrenchingly sombre textures of 2012's Valtari. Kveikur only expels its heavy post-rock tones in short bursts, as its dark undercurrents are cleverly balanced against the band’s ever-so-slight pop sensibilities.

This quiet, gentle side to the band sat right in the foreground of Valtari, yet Kveikur recalls even more clearly the dark aesthetic of the group’s debut album, 1997's Von. There’s a recurring tension created by the album’s attempts to balance the heavy, rolling and powerful percussion of Orri Páll Dýrason with the sweet, pop-inflected vocals of frontman Jón “Jónsi” Þór Birgisson.

Now a trio, following the departure of founding member Kjartan Sveinsson, Sigur Rós use this tension to great effect on Kveikur. Opening track Brennisteinn is one of the heaviest, most texturally dense pieces the band has ever created. It is immediately gripping, layered with the muddy fuzz bass of Georg Holm, Jónsi’s bowed guitar work and a momentous reverberating drum-line. For all its sonic and emotional power, though, Brennisteinn remains the central microcosm of Kveikur – it foreshadows an album with a dark undercurrent, yet one which can also revert to being elegant, soothing and ornate.

The pop tendencies which became so apparent on 2008's Með suð í eyrum við spilum endalaust leak through Kveikur‘s danceable art-rock. Tracks Ísjaki and Stormur both carry such momentum, driven by percussion but circling around Jónsi’s vocal hooks. The tone inevitably reverts with the start of the album’s title track. Whilst those relentless, rolling drum lines and distorted guitars remain central, there’s a tremendous sense of space created by such a texturally dense sound. A space which grows and grows only to beautifully self-destruct.

Don’t let the hauntingly dark cover-art throw you – Kveikur doesn’t just work in black and whites. This is an album with personality and an unassuming, bittersweet warmth. It may not be the most accessible release in the Sigur Rós discography, but it harks back to the sounds which buoyed their rise into popular music, and also revives the vitality and power of dense post-rock. The prospect of a whole album filled solely with “aggressive” tracks like Brennisteinn and Kveikur, whilst exciting, was an unlikely outcome, as it may have alienated more than a few new listeners – perhaps those introduced to the subtleties of Sigur Rós via The Simpsons. So let’s hope that any newcomers don’t tune-out mid-way through the explicit sting of Kveikur‘s first track. What a waste that would be.